The present invention relates to small internal combustion engines, especially those utilizing a carburetor, such as engines in a lawnmower or a snow blower. Cold temperature starting of the engine requires a more fuel-rich fuel-air mixture in the intake manifold of the engine to sustain the combustion reaction. In some engines, this is done by closing a choke valve, thereby partially choking off the air supply to the engine. As the engine warms up, the choke is no longer necessary because the increased temperatures in the engine help to sustain the combustion reaction and thus the choke is opened, allowing more air into the intake manifold. In many small engines, the choke valve is actuated manually.
Typically during warm engine restarts, the choke must remain open to start the engine and to prevent the engine from stumbling or stalling. During cold starts, if the choke valve is opened too soon, the engine may stall because the fuel-air mixture is not rich enough to sustain the reaction. If the choke remains closed too long, the engine may also stumble and excessive hydrocarbon emissions and fouling of the spark plugs can occur.